Spatiotemporal assessment of wetlands and land reclaim activities in Eastern Lagos State Nigeria

Abstract

This paper presents a spatiotemporal assessment of sand-filling practices and their environmental implications in eastern Lagos over a  four-decade period (1984-2024). Multispectral Landsat TM images at ten-year intervals namely, 1984, 1994, 2004 and 2024 were obtained  from the Sentinel hub and subjected to supervised classification to assess land area that was reclaimed over time. The classification  revealed a significant shift in land cover categories; areas built-up, expanded from 6035.92 hectares in 1984 to 18002.77 hectares in 2024, while vegetation and water bodies decreased from 19351.48 to 9180.79 and from 29355.12 to 27341.49 hectares respectively. The area  occupied by the sand-filled category was 508.85 in 1984, 2528.79 in 1994, 943.19 in 2004, 600.50 in 2014 and 726.95 in 2024. The cumulative  area of sand-filled in forty years is 5308.28 hectares. Sand-filled areas were always converted to buildings after some years of  consolidation, hence the lack of a particular trend in coverage over time. Sand filling activities are primarily driven by urbanization and  infrastructure development, and they are intensified along the eastern coastline of Lagos, particularly from Victoria Island to Lekki. The  ecological and environmental consequences of sand filling, include habitat loss, shoreline erosion, increased land surface temperatures  (LST) and vegetation loss. The regression coefficients showed that every unit increase in the LST led to a 0.08 unit reduction in the  vegetation index for 2004 and 2014, and a one unit rise in the LST led to a 0.1 unit reduction in the vegetation index value for 2024. This paper concludes with emphasis on the key role of remote sensing in monitoring sand-filling dynamics, guiding policy interventions, and  promoting sustainable urban growth.